1. Field of the Invention
The present invention relates generally to image forming machines and, more particularly, to a fuser for an image forming machine with end caps having protuberances strategically placed on an inner flange for reducing belt skew.
2. Description of the Related Art
An image forming machine, such as a printer, copier, fax machine, all-in-one device or a multifunctional device, typically includes a heating device, such as a fuser, to fix a developing agent, such as toner, to a media sheet. The fuser typically contains a heater and an endless belt and backup pressure roll that form a nip for the media sheet to pass through. They provide heat and/or pressure to the toner to soften the toner so that it will adhere to the media sheet. The fuser belt defines an inner loop. The heater is positioned within the inner loop and in direct contact with the belt. The heater has a profile generally corresponding to the travel path of the belt to provide an area contact rather than a line contact for more efficient thermal transfer. The heater is in the form of a ceramic heater held in a heater housing positioned within the inner loop and against the belt. The fuser belt is an “idling belt” having no drive rolls within it. The belt is driven by the rotation of the backup pressure roll, through the driving association of the belt with the pressure roll at the nip.
The location of the belt is controlled by an end cap attached to each end of the heater housing. The end cap has an inner flange that limits the left to right axial movement of the belt. The backup pressure roll rotates which, in turn, rotates the belt and drives the print media through the fuser nip. The end caps do not rotate.
Sometimes the belt in the fuser skews with respect to the fuser backup pressure roll and the end caps. The belt skew results from differences in friction along the heater. This misalignment allows the belt to infringe on the media path as it enters the fuser nip causing smudging on the printed page that results in unacceptable print quality. Another phenomenon that belt skew affects is the “left to right” movement of the media as it passes through the fuser nip. This is known as “media walk” and is defined as the distance in millimeters the paper moves side to side. Excessive media walk may cause the media to crash into limiting features within the printer's paper path.
Thus, there is still a need for an innovation that will reduce skew between the end caps and the belt so as to reduce belt skew with the backup pressure roll.